R1:f3d5e22a4505

Destroy associated worker tasks and notifications

Summary: Fixes T7107. When destroying an object, destroy associated worker tasks and notifications.

Test Plan:
# Manually updated the `phabricator_worker.worker_activetask` table by setting `objectPHID` to the desired object.
# Removed object with `./bin/remove destroy`.
# Queried `phabricator_worker.worker_activetask` table.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest…